Guess who's back on 'Lost'! But why?

WEST HOLLYWOOD, Calif. — So Michael is on the boat, but what’s he been up to all this time?

‘‘I wish I could tell you,’’ actor Harold Perrineau said in an interview.

It’s the question that’s nagged ‘‘Lost’’ viewers since the tormented single father castaway played by Perrineau sailed away with his son from the ABC drama at the end of the second season — and didn’t return at any point during the third.

Although he’s been listed as a cast member throughout the current fourth season, Perrineau didn’t appear onscreen until Thursday, when Michael was introduced as a deck-swabbing crewman named Kevin Johnson on that mysterious freighter that’s been drifting off the coast and apparently giving those aboard a deadly case of cabin fever.

Viewers will find out where Michael has been for the past season and a half — about half a month in island time — during the March 20 episode, which was filmed last year before the writer’s strike forced ABC to shut down production.

The Michael-centric episode — or should we call him Kevin now? — will feature flashbacks detailing what happened after Perrineau’s character shockingly gunned down fellow passengers Ana-Lucia and Libby in order to release seemingly evil Ben and retrieve his son Walt from captivity.

‘‘I hope people see Michael’s return and think, ’Oh, this is gonna be good,’’’ Perrineau said over lunch Wednesday. ‘‘I hope they think this ride is good. We busted our butts doing this one. It felt like we were making a movie because there’s so much stuff that happens in this episode.’’

Getting the rest of the Michael-related ‘‘Lost’’ questions out of the way: Was Michael ever able to get back home to New York? Will his son also return to the show? And was he the man in the coffin during that jaw-dropping flashfoward at the end of season three? According to Perrieanu, the answers are yes, maybe and he has no idea.

‘‘Oh, I thought for sure it was Michael in the coffin,’’ he said. ‘‘But I still don’t know.’’

Perrineau, whose ‘‘Lost’’ return was triumphantly teased at Comic-Con 2007, says the show’s writers have kept him just as clueless as the audience. He hasn’t read any scripts for the six planned post-strike episodes. However, that doesn’t mean viewers should expect less Michael after next week. Perrineau was scheduled to report to set in Hawaii following Wednesday’s interview.

‘‘I know I’ll be there until the end of the season,’’ he said. ‘‘I have no idea if it goes beyond that or not.’’

The 44-year-old actor from New York tenses up when he talks about the third season. Perrineau was the only one of the 14 original ‘‘Lost’’ cast members to not appear in a third-season flashback, mind-bending vision or otherwise. He says he ‘‘wasn’t so happy’’ about the creative decision to leave Michael and Walt off the island and focus on others.

‘‘I was hurt, really hurt,’’ said Perrineau. ‘‘I told myself I had to watch the show, so I at least knew what was going on in case I was brought back, but then I was like, ’Why?’ I never knew what was going on before. Why should I start trying to figure it out now?’’

Instead of waiting by the phone to hear if his character would return to the series, Perrineau moved on to other projects, including a part in the film ‘‘28 Weeks Later’’ and a role in the CBS pilot ‘‘Demons.’’ When ‘‘Demons’’ didn’t get picked up, that made room in Perrineau’s schedule to get ‘‘Lost’’ again.

‘‘I started with ’Lost,’ so I really want to see Michael until the end,’’ says Perrineau. ‘‘I don’t know what that means. I guess I won’t know what that means until the end. I just know I didn’t want Michael and Walt to get on that boat and that be it. That didn’t seem so cool.’’

Perrineau believes ‘‘Lost’’ masterminds Carlton Cuse and Damon Lindelof really do have a plan for Michael, and he thinks it might finally come together now that he’s returned to fray. Of all the questions Perrineau has about his character, the one thing he’s most interested to know is surprisingly simple.

‘‘It seems like all the other characters on the island have dealt with redemption, in some form or another,’’ said Perrineau. ‘‘But not Michael. He’s only ever contended with being a father. The thing I want to know is: Why was Michael put on the island in the first place?’’